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Complete description on softwre development life cycle
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3/18/2014 Software development process - Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Software_development_process 1/8
Software development processFrom Wikipedia, the free encyclopedia
A software development process, also known as a software development life-cycle (SDLC), is a structureimposed on the development of a software product. Similar terms include software life cycle and softwareprocess. It is often considered a subset of systems development life cycle. There are several models for suchprocesses, each describing approaches to a variety of tasks or activities that take place during the process. Somepeople consider a life-cycle model a more general term and a software development process a more specific term.For example, there are many specific software development processes that 'fit' the spiral life-cycle model. ISO/IEC12207 is an international standard for software life-cycle processes. It aims to be the standard that defines all thetasks required for developing and maintaining software.
Contents
1 Overview
2 Software development activities
2.1 Planning2.2 Implementation, testing and documenting
2.3 Deployment and maintenance
3 Software development models
3.1 Waterfall model
3.2 Spiral model
3.3 Iterative and incremental development3.4 Agile development
3.5 Rapid application development
3.6 Code and fix
4 Process improvement models
5 Formal methods6 See also
6.1 Development methods
6.2 Related subjects7 References
8 External links
Overview
Software development organizations implement process methodologies to ease the process of development.Sometimes, contractors may require methodologies employed, an example is the U.S. defense industry, whichrequires a rating based on process models to obtain contracts.
The international standard for describing the method of selecting, implementing and monitoring the life cycle forsoftware is ISO/IEC 12207.
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A decades-long goal has been to find repeatable, predictable processes that improve productivity and quality.Some try to systematize or formalize the seemingly unruly task of designing software. Others apply projectmanagement techniques to designing software. Without effective project management, software projects can easilybe delivered late or over budget. With large numbers of software projects not meeting their expectations in terms offunctionality, cost, or delivery schedule, it is effective project management that appears to be lacking.
Organizations may create a Software Engineering Process Group (SEPG), which is the focal point for processimprovement. Composed of line practitioners who have varied skills, the group is at the center of the collaborativeeffort of everyone in the organization who is involved with software engineering process improvement.
Software development activities
Planning
Planning is an objective of each and every activity, where we want to discover things that belong to the project. An
important task in creating a software program is extracting the requirements or requirements analysis.[1] Customerstypically have an abstract idea of what they want as an end result, but do not know what software should do.Skilled and experienced software engineers recognize incomplete, ambiguous, or even contradictory requirementsat this point. Frequently demonstrating live code may help reduce the risk that the requirements are incorrect.
Once the general requirements are gathered from the client, an analysis of the scope of the development should bedetermined and clearly stated. This is often called a scope document.
Certain functionality may be out of scope of the project as a function of cost or as a result of unclear requirementsat the start of development. If the development is done externally, this document can be considered a legaldocument so that if there are ever disputes, any ambiguity of what was promised to the client can be clarified.
Implementation, testing and documenting
Implementation is the part of the process where software engineers actually program the code for the project.
Software testing is an integral and important phase of the software development process. This part of the processensures that defects are recognized as soon as possible.
Documenting the internal design of software for the purpose of future maintenance and enhancement is donethroughout development. This may also include the writing of an API, be it external or internal. The softwareengineering process chosen by the developing team will determine how much internal documentation (if any) isnecessary. Plan-driven models (e.g., Waterfall) generally produce more documentation than Agile models.
Deployment and maintenance
Deployment starts directly after the code is appropriately tested, approved for release, and sold or otherwisedistributed into a production environment. This may involve installation, customization (such as by setting
parameters to the customer's values), testing, and possibly an extended period of evaluation.[citation needed]
Software training and support is important, as software is only effective if it is used correctly.[citation needed]
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The activities of the software
development process represented in
the waterfall model. There are several
other models to represent this
process.
Maintaining and enhancing software to cope with newly discovered faults or requirements can take substantial time
and effort, as missed requirements may force redesign of the software.[citation needed]
Software development models
Several models exist to streamline the development process. Each one has its pros and cons, and it is up to thedevelopment team to adopt the most appropriate one for the project. Sometimes a combination of the models maybe more suitable.
Waterfall model
Main article: Waterfall model
The waterfall model shows a process, where developers have to followthese phases in order:
1. Requirements specification (Requirements analysis)2. Software design
3. Implementation and Integration4. Testing (or Validation)
5. Deployment (or Installation)6. Maintenance
In a strict Waterfall model, after each phase is finished, it proceeds to thenext one. Reviews may occur before moving to the next phase whichallows for the possibility of changes (which may involve a formal changecontrol process). Reviews may also be employed to ensure that thephase is indeed complete; the phase-completion criteria are oftenreferred to as a "gate" that the project must pass through to move to thenext phase. Waterfall discourages revisiting and revising any prior phase once it's complete. This "inflexibility" in apure Waterfall model has been a source of criticism by supporters of other more "flexible" models.
The Waterfall model is also commonly taught with the mnemonic A Dance in the Dark Every Monday, representing
Analysis, Design, Implementation, Testing, Documentation and Execution, and Maintenance.[citation needed]
Spiral model
Main article: Spiral model
The key characteristic of a Spiral model is risk management at regular stages in the development cycle. In 1988,Barry Boehm published a formal software system development "spiral model," which combines some key aspect ofthe waterfall model and rapid prototyping methodologies, but provided emphasis in a key area many felt had beenneglected by other methodologies: deliberate iterative risk analysis, particularly suited to large-scale complexsystems.
The Spiral is visualized as a process passing through some number of iterations, with the four quadrant diagramrepresentative of the following activities:
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Spiral model (Boehm, 1988)
1. Formulate plans to: identify software targets, implement the program, clarify the project development
restrictions
2. Risk analysis: an analytical assessment of selected programs, to consider how to identify and eliminate risk3. Implementation of the project: the implementation of software development and verification
Risk-driven spiral model, emphasizing the conditions of options and constraints in order to support software reuse,software quality can help as a special goal of integration into the product development. However, the spiral modelhas some restrictive conditions, as follows:
1. The spiral model emphasizes risk analysis, and thus requires
customers to accept this analysis and act on it. This requires both
trust in the developer as well as the willingness to spend more to
fix the issues, which is the reason why this model is often used forlarge-scale internal software development.
2. If the implementation of risk analysis will greatly affect the profits
of the project, the spiral model should not be used.3. Software developers have to actively look for possible risks, and
analyze it accurately for the spiral model to work.
The first stage is to formulate a plan to achieve the objectives with theseconstraints, and then strive to find and remove all potential risks throughcareful analysis and, if necessary, by constructing a prototype. If some risks cannot be ruled out, the customer hasto decide whether to terminate the project or to ignore the risks and continue anyway. Finally, the results areevaluated and the design of the next phase begins.
Iterative and incremental development
Main article: Iterative and incremental development
Iterative development[2] prescribes the construction of initially small but ever-larger portions of a software projectto help all those involved to uncover important issues early before problems or faulty assumptions can lead todisaster.
Agile development
Main article: Agile software development
Agile software development uses iterative development as a basis but advocates a lighter and more people-centricviewpoint than traditional approaches. Agile processes fundamentally incorporate iteration and the continuousfeedback that it provides to successively refine and deliver a software system.
There are many variations of agile processes:
In extreme programming (XP), the phases are carried out in extremely small (or "continuous") steps
compared to the older, "batch" processes. The (intentionally incomplete) first pass through the steps mighttake a day or a week, rather than the months or years of each complete step in the Waterfall model. First,
one writes automated tests, to provide concrete goals for development. Next is coding (by a pair of
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Rapid Application Development
(RAD) Model
programmers), which is complete when all the tests pass, and the programmers can't think of any more teststhat are needed. Design and architecture emerge from refactoring, and come after coding. The same people
who do the coding do design. (Only the last feature — merging design and code — is common to all theother agile processes.) The incomplete but functional system is deployed or demonstrated for (some subset
of) the users (at least one of which is on the development team). At this point, the practitioners start again on
writing tests for the next most important part of the system.[3]
Dynamic systems development method
Scrum
Rapid application development
Rapid application development R.A.D is a software developmentmethodology that uses minimal planning in favor of rapid prototyping. The"planning" of software developed using RAD is interleaved with writingthe software itself. The lack of extensive pre-planning generally allowssoftware to be written much faster, and makes it easier to changerequirements. RAD involves methods like iterative development andsoftware prototyping. According to Whitten (2004), it is a merger ofvarious structured techniques, especially data-driven InformationEngineering, with prototyping techniques to accelerate software systems
development.[4]
In rapid application development, structured techniques and prototypingare especially used to define users' requirements and to design the final system. The development process startswith the development of preliminary data models and business process models using structured techniques. In thenext stage, requirements are verified using prototyping, eventually to refine the data and process models. Thesestages are repeated iteratively; further development results in "a combined business requirements and technical
design statement to be used for constructing new systems".[4]
Code and fix
"Code and fix" development is not so much a deliberate strategy as an artifact of naïveté and schedule pressure on
software developers.[5] Without much of a design in the way, programmers immediately begin producing code. Atsome point, testing begins (often late in the development cycle), and the unavoidable bugs must then be fixed beforethe product can be shipped. See also: Continuous integration and Cowboy coding.
Process improvement models
Capability Maturity Model Integration
The Capability Maturity Model Integration (CMMI) is one of the leading models and based on best practice.Independent assessments grade organizations on how well they follow their defined processes, not on the
quality of those processes or the software produced. CMMI has replaced CMM.
ISO 9000ISO 9000 describes standards for a formally organized process to manufacture a product and the methods
of managing and monitoring progress. Although the standard was originally created for the manufacturing
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sector, ISO 9000 standards have been applied to software development as well. Like CMMI, certificationwith ISO 9000 does not guarantee the quality of the end result, only that formalized business processes have
been followed.
ISO/IEC 15504
ISO/IEC 15504 Information technology — Process assessment also known as Software Process
Improvement Capability Determination (SPICE), is a "framework for the assessment of software processes".This standard is aimed at setting out a clear model for process comparison. SPICE is used much like
CMMI. It models processes to manage, control, guide and monitor software development. This model is
then used to measure what a development organization or project team actually does during softwaredevelopment. This information is analyzed to identify weaknesses and drive improvement. It also identifies
strengths that can be continued or integrated into common practice for that organization or team.
Formal methods
Formal methods are mathematical approaches to solving software (and hardware) problems at the requirements,specification, and design levels. Formal methods are most likely to be applied to safety-critical or security-criticalsoftware and systems, such as avionics software. Software safety assurance standards, such as DO-178B, DO-178C, and Common Criteria demand formal methods at the highest levels of categorization.
For sequential software, examples of formal methods include the B-Method, the specification languages used inautomated theorem proving, RAISE, and the Z notation.
Formalization of software development is creeping in, in other places, with the application of Object ConstraintLanguage (and specializations such as Java Modeling Language) and especially with model-driven architectureallowing execution of designs, if not specifications.
For concurrent software and systems, Petri nets, process algebra, and finite state machines (which are based onautomata theory - see also virtual finite state machine or event driven finite state machine) allow executable softwarespecification and can be used to build up and validate application behavior.
Another emerging trend in software development is to write a specification in some form of logic—usually avariation of first-order logic (FOL)—and then to directly execute the logic as though it were a program. The OWLlanguage, based on Description Logic (DL), is an example. There is also work on mapping some version of English(or another natural language) automatically to and from logic, and executing the logic directly. Examples areAttempto Controlled English, and Internet Business Logic, which do not seek to control the vocabulary or syntax.A feature of systems that support bidirectional English-logic mapping and direct execution of the logic is that theycan be made to explain their results, in English, at the business or scientific level.
See also
Development methods
Chaos model
Extreme Programming
ICONIX (UML-based object modeling with
Related subjects
Bachelor of Science in Information Technology
Best coding practices
Conceptual model
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use cases)
Incremental funding methodology
Model-driven engineering
Service-oriented modeling
Software prototyping
Specification and Description Language
Top–down and bottom–up design
Unified ProcessUser experience
V-Model (software development)
Verification and Validation (software)
Cost estimation in software engineeringIPO Model
List of software development philosophies
Method engineering
Outline of software engineering
Performance engineering
Process (computing)
Programming paradigmProgramming productivity
Project
Rapid application development
Service-oriented modeling
Software design
Software development
Software documentationSoftware release life cycle
Systems design
Systems Development Life Cycle
Test effort
References
1. ^ Ralph, P., and Wand, Y. A Proposal for a Formal Definition of the Design Concept. In, Lyytinen, K.,Loucopoulos, P., Mylopoulos, J., and Robinson, W., (eds.), Design Requirements Engineering: A Ten-YearPerspective: Springer-Verlag, 2009, pp. 103-136
2. ^ ieeecomputersociety.org (http://doi.ieeecomputersociety.org/10.1109/MC.2003.1204375)
3. ^ Kent Beck, Extreme Programming, 2000.
4. ̂a b Whitten, Jeffrey L.; Lonnie D. Bentley, Kevin C. Dittman. (2003). Systems Analysis and Design Methods. 6thedition. ISBN 0-256-19906-X.
5. ^ McConnell, Steve. "7: Lifecycle Planning". Rapid Development. Redmond, Washington: Microsoft Press. p. 140.
External links
Gerhard Fischer, "The Software Technology of the 21st Century: From Software Reuse to Collaborative
Software Design" (http://l3d.cs.colorado.edu/~gerhard/papers/isfst2001.pdf), 2001Lydia Ash: The Web Testing Companion: The Insider's Guide to Efficient and Effective Tests, Wiley,
May 2, 2003. ISBN 0-471-43021-8
SaaSSDLC.com (http://SaaSSDLC.com/) — Software as a Service Systems Development Life Cycle
Project
Software development life cycle (SDLC) [visual image], software development life cycle
(http://www.notetech.com/images/software_lifecycle.jpg)
Heraprocess.org (http://www.heraprocess.org/) — Hera is a light process solution for managing webprojects
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Categories: Software development process Formal methods Methodology Software engineering
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